The subject invention relates generally to vibration damping of suspension and steering systems in a motor vehicle. More specifically, the subject invention relates to vibration damping using viscous sheer and magneto-rheological clutching.
Rotary dampers have been installed in both steering and suspension assemblies of motor vehicles to dampen the amount of vibration detected by the vehicle operator from such variables as vehicle speed, road bumps, wheel alignment, wheel chatter, and tread wear. Rotary dampers of this type reduce the amount of vibration transferred to the vehicle operator by resisting rotational velocity generated from a pinion associated with either the steering assembly or the suspension assembly. The rotational velocity is resisted by torque generated by the rotary damper thereby reducing vibration. The torque is derived from a clutch-like resistance generated by a fluid, having a Newtonian behavior, when a rotor disposed within the vibration damper assembly is operatively connected to the pinion and receives rotational velocity from the pinion.
The rotational velocity generated by the pinion connected to the rotary damper varies with the amount of vibration absorbed from the operating variables listed above. A different level of torque is required to provide uniform dampening at high rotational velocities than at low rotational velocities. A Newtonian fluid provides adequate torque at low rotational velocity, however, at high rotational velocities, too much torque is provided by the Newtonian fluid, which reduces the effectiveness of the rotary damper.
Therefore, it would be desirable to provide a rotary damper having variable torque capabilities that would optimize the amount of vibration damping at both low and high rotational velocity.
The present invention discloses a vibration damper assembly for reducing the amount of vibration transferred to a motor vehicle operator from variables such as vehicle speed, road bumps, wheel alignment, wheel chatter, and tread wear.
The assembly includes a rotor disposed within a housing. The rotor is operatively connected to a rotational velocity generating member, such as a pinion, that is connected to a steering or suspension assembly. A conductive sleeve is positioned between the housing and the rotor. A coil is positioned adjacent the sleeve and is capable of generating a magnetic field that is transmitted through the sleeve. An annular plate separates the rotor from the sleeve and defines a viscous chamber and a Magneto-Rheological (MR) fluid chamber. The viscous chamber is disposed between the sleeve and the housing and the MR chamber is disposed between the sleeve and the rotor. A viscous fluid is contained within the viscous chamber and an MR fluid is contained within the MR chamber. The viscous fluid behaves as a Newtonian fluid throughout operation of the assembly. The MR fluid behaves as a Bingham plastic when it is subjected to the magnetic field and otherwise, behaves as a Newtonian fluid.
The subject concept overcomes the deficiencies of the prior art by providing the ability to vary the amount of torque generated by the vibration damper assembly. When not subjected to the magnetic field, the torque is generated by a Newtonian fluid, which is preferable at low velocity. When subjected to the magnetic field, the MR fluid is transformed from a fluid having Newtonian characteristic to a fluid having Bingham plastic characteristics, which generates a torque that is preferable at higher velocities.